Implementation:Datahub project Datahub FieldPath Schematron

Knowledge Sources	Datahub_project_Datahub
Domains	Schema_Conversion, Field_Path_Modeling
Last Updated	2026-02-10 00:00 GMT

Overview

Description

FieldPath is a model class in the SchemaTron library that represents the hierarchical path to a field within a DataHub schema. It maintains an ordered list of FieldElement objects, each representing one level in the field hierarchy, and provides methods for path manipulation and serialization.

Key capabilities:

• V2 path formatting -- Automatically determines whether to use v2 path format (prefixed with [version=2.0]) based on schema complexity (union/array types present) or explicit configuration.
• Key schema support -- Adds a [key=True] prefix for key schema fields.
• Path manipulation -- Supports cloning with additional elements (clonePlus), removing the last element (popLast), and expanding type information (expandType).
• Parent type tracking -- Maintains an optional DataHubType parent type on the last element, enabling type override for native type rendering (arrays and maps).
• Recursive type detection -- Can detect recursive type references by matching schema strings against path elements.

The EMPTY_FIELD_NAME constant (a single space) is used as a sentinel for fields that need a name but do not have one.

Usage

Used throughout the SchemaTron schema conversion pipeline to build and manipulate field paths during Avro-to-DataHub schema translation. The asString() method produces the final dot-separated field path string stored in SchemaField.fieldPath.

Code Reference

Source Location

metadata-integration/java/datahub-schematron/lib/src/main/java/io/datahubproject/schematron/models/FieldPath.java

Signature

@Data
public class FieldPath {

    public static final String EMPTY_FIELD_NAME = " ";

    @NonNull private List<FieldElement> path;
    private boolean isKeySchema;
    private boolean useV2PathsAlways;

    public FieldPath()

    public void setPath(List<FieldElement> path)

    public String getRecursive(Map<String, Object> schema)

    public FieldPath popLast()

    public FieldPath clonePlus(FieldElement element)

    public FieldPath expandType(String type, Object typeSchema)

    public boolean hasFieldName()

    public boolean ensureFieldName()

    public String asString()

    public String dump()
}

Import

import io.datahubproject.schematron.models.FieldPath;

I/O Contract

Inputs

Method	Parameter	Type	Description
Constructor	(none)	--	Creates an empty path with useV2PathsAlways=true
setPath	path	List<FieldElement>	Replaces the path elements (no nulls allowed)
clonePlus	element	FieldElement	Element to append to a cloned path
expandType	type	String	Type name to add to the last element
expandType	typeSchema	Object	Schema object whose string form is recorded
getRecursive	schema	Map<String, Object>	Schema map to match against for recursion detection

Outputs

Method	Return Type	Description
asString()	String	The formatted field path (e.g., [version=2.0].[type=union].fieldName)
popLast()	FieldPath	New FieldPath with the last element removed
clonePlus()	FieldPath	New FieldPath with an additional element appended
expandType()	FieldPath	New FieldPath with expanded type info on the last element
getRecursive()	String (nullable)	The matched type name if recursion is detected, null otherwise
hasFieldName()	boolean	Whether any element in the path has a non-null name
dump()	String	Debug string showing the full path with element details

Usage Examples

// Build a field path
FieldPath path = new FieldPath();
FieldPath extended = path.clonePlus(new FieldElement(
    new ArrayList<>(List.of("record")),
    new ArrayList<>(List.of(schemaStr)),
    "myField",
    null));

// Convert to string
String fieldPathStr = extended.asString();
// e.g., "[version=2.0].[type=record].myField"

// Expand type for union
FieldPath withUnion = extended.expandType("union", unionSchema);

// Check for recursive types
String recursiveType = path.getRecursive(schemaMap);

Related Pages

• Datahub_project_Datahub_SchemaTronDataHubType -- Used as parent type for path elements to determine native type overrides
• Datahub_project_Datahub_SchemaTron_CLI -- CLI tool that drives the schema conversion using FieldPath